1. Field of the Invention
The present invention relates generally to the field of devices which close the space between the lower end of a closed door and the door threshold to prevent air from passing underneath the door. More specifically the present invention relates to a door lower end sealing apparatus including a gate member which is automatically raised through horizontal movement of a slide bar by opening the door to permit the door to swing freely, and which is automatically lowered by closing the door to seal the space between the threshold and the lower end of the door while the door is closed. A series of leaf springs interconnect the gate member and the slide bar, each leaf spring having a circular loop segment at its upper end and its lower ends. The lower loop segment is snugly fitted into a circular notch in the gate member upper surface and each spring angles upwardly and laterally and is engagingly fitted into a slide bar circular notch in the lower surface of the slide bar. The slide bar is mounted on an upright mounting member and constrained to slide horizontally only, and the gate member is mounted to the mounting member and constrained to slide vertically only.
Closing the door causes the door frame to depress a protruding end of the slide bar. This action slides the slide bar horizontally in one lateral direction and causes the middle segments of the pivot springs to swing vertically upright against biasing of the springs, increasing the vertical extent of the springs and thereby separating the slide bar and gate member so that the gate member advances downwardly into contact with the floor at the point at which the door reaches a fully closed position. Opening the door permits the lateral resilient force of the pivot leaf springs to drive the slide bar in the other lateral direction so that the protruding end once again protrudes from the side of the door. The leaf springs pivot horizontally into their initial angled position, lifting the gate member into its non-sealing position. The apparatus may be mounted on a lower face of the door or within the door lower end.
2. Description of the Prior Art
There have long been sealing devices for closing the gap between the lower end of a door and the threshold, to prevent the passage of heated or cooled air for savings in energy costs. These devices have generally been complex and expensive to manufacture.
One such prior device is that of Beck, U.S. Pat. No. 2,433,331, issued on Dec. 30, 1947. Beck teaches a door bottom closing and sealing device contained within a channel structure which is secured to the lower end of a door. Beck includes a channel structure containing a sealing gate which is loosely suspended from a horizontal spring member. One end of the spring member is fixed and the other end protrudes laterally from the door. When the door is opened, the elastic memory of the spring member straightens the spring member and thereby raises and holds the sealing gate in an elevated position. When the door is closed, the door frame abuts and depresses the spring member protruding end and thus bows the spring member downwardly, lowering the attached sealing gate into contact with the floor. A problem with Beck is that the single holding point, free swinging sealing gate might rattle within the channel structure, making the door seem rickety. Another problem is that the loose suspension of the sealing gate makes the apparatus sloppy, weak and prone to failure.
Wexler, U.S. Pat. No. 4,947,584, issued on Aug. 14, 1990, discloses an automatic door bottom. A downward opening horizontal channel member is provided at the base of a door and contains a drop bar for making sealing contact with the floor. A push rod protrudes laterally from the door and is depressed by the door frame when the door is closed. Depressing the push rod causes a horizontal spring member much like that of Beck to bow downwardly, thereby lowering the attached drop bar. Magnets cause one end of the drop bar to descend before the other. The resilient action of the spring member raises the drop bar off the floor when the door is opened, and the push rod is freed to again protrude. The problems of Beck are again presented.
Christensen, U.S. Pat. No. 4,425,738, issued on Jan. 17, 1984, teaches an automatic threshold seal for a door. Christensen is just another downwardly bowing axially compressed leaf spring structure with a protruding end and a suspended gate; as is Rivers, U.S. Pat. No. 3,703,788, issued on Nov. 28, 1972, which discloses an automatic door bottom; and Ellingson, Jr., U.S. Pat. No. 3,871,133, issued on Mar. 18, 1975, which teaches a door bottom weather sealing structure.
Berndt, Jr., U.S. Pat. No. 4,406,088, issued on Sep. 27, 1983, reveals a door bottom sealing apparatus. Berndt, Jr. includes an inverted channel member secured to the inner face of a door, at the bottom end of the door. A sealing member is pivotally retained within the channel member by a series of hanger linkages secured at their lower ends to the sealing member and at their upper ends to the channel member. Torsion springs bias the sealing member into an upward and laterally displaced position such that an end of the sealing member protrudes toward the door jamb. Closing the door depresses the protruding end of the sealing member and thereby pivots the sealing member downwardly on the hanger linkages to make contact with the floor. Opening the door frees the protruding end so that the torsion springs pivot the sealing member back to its elevated rest position. A problem with Berndt, Jr. is that the protruding end of the sealing member moves a pre-set, fixed distance when depressed and thus lowers the sealing member a constantly repeating fixed distance. Should some object obstruct the lowering of the sealing member, the closing of the door could damage the apparatus. Another problem is that the sealing member moves laterally as well as downwardly, making abrading sliding contact with the floor.
Ohi, U.S. Pat. No. 4,805,345, issued on Feb. 21, 1989teaches a sealing device for a door. Ohi includes a drive bolt with a protruding end, and a pivoting linkage connected to the drive bolt and to a sealing gate. Closing the door depresses the protruding end and pivots the linkage to lower the sealing gate into contact with the floor. The distance the drive bolt is moved upon closing of the door is adjustable by rotating a tubular screw at the drive bolt protruding end. Despite this adjustability, the unexpected presence of an object below the door could cause damage, as indicated above for Berndt, Jr. Ohi is also relatively complex and expensive to manufacture.
Wetzel, U.S. Pat. No. 3,250,314, issued on May 10, 1966, discloses a seal for a folding partition, recessed into a channel within a door lower end. As disclosed in Berndt, Jr. and in Ohi, a sealing member is suspended from downwardly pivoting hanger linkages and lowered by action of a protruding bolt assembly. The problems of Berndt, Jr. are again presented.
Hawk, U.S. Pat. No. 2,033,241, issued on Mar. 10, 1936, reveals an automatic weather strip for preventing passage of rain, dust and hot or cold air beneath a door or window. The Hawk design is unusual in that no laterally protruding bolt assembly is provided. Instead a series of camming ramps are secured to the threshold beneath the door closed position. Vertical lift rods protrude down through the bottom of the door to ride up on these ramps when the door is closed, against the biasing of coil springs around the rods. An arm protrudes laterally from each rod toward a face of the door, and is connected to a pivoting sealing strip protruding out through a slot in the lower face of the door. Riding up on the ramps as the door closes lifts the rods, the arms and the inner edge of the sealing strip, pivoting the outer edge of the sealing strip downwardly into sealing contact with the threshold. A problem with Hawk is that the pivoting sealing strip structure is relatively delicate, and it could be damaged by abrupt contact with an obstacle in the path of the door. Another problem is that the downwardly protruding rods might touch and scratch the floor as the door swings.
It is thus an object of the present invention to provide a door sealing apparatus which automatically closes the gap between the door lower end and the threshold each time the door is closed.
It is another object of the present invention to provide such an apparatus which biases but does not force a sealing gate member toward a sealing position, so that an obstruction on the floor or threshold does not damage the apparatus.
It is still another object of the present invention to provide such an apparatus with a sealing gate member which cannot slide laterally during lowering and raising to minimize sliding and abrading contact with the threshold.
It is finally an object of the present invention to provide such an apparatus which is sturdy, simple and reliable in design, and relatively inexpensive to manufacture.